dfb76c1e15 Use doc(notable_trait) (Tobin C. Harding)
Pull request description:
There is an unstable feature that puts up a little 'i' in a circle next to any function that returns a type that implements an notable trait. For us this means we can make the extension traits more discoverable.
ref: https://doc.rust-lang.org/unstable-book/language-features/doc-notable-trait.htmlClose: #3232
ACKs for top commit:
apoelstra:
ACK dfb76c1e15933fe0058c1bb69c4b1b9acddceee8; successfully ran local tests
Tree-SHA512: 0fbc7a2a3c8c499a9276d1e86b9966a7ae6bd8a354aff5fd40aa11d07945db589b2a9c2cdfa43ddadfafcee706ae7f68cedc269f74622643307cc43cd07d554f